A variety of useful silicone compositions cure at room temperature to elastomeric materials which possess a broad spectrum of physical and chemical properties. These compositions are particularly desirable because they surface cure in thirty minutes or less after exposure to the atmosphere but remain substantially soft for years. They also adhere tenaciously to a wide variety of materials such as glass, porcelain, wood, metal and organic plastics. Because of this, they are adaptable for practically any type of sealant application including building and automotive equipment applications. The following patents discuss some of these compounds in more detail.
U.S. Pat. No. 3,189,576 to Sweet describes oxime silanes useful in the manufacture of room temperature curing compositions. Specifically, Sweet teaches trifunctional and tetrafunctional ketoximino silanes as crosslinkers and their use in the manufacture of room temperature curing silicone elastomeric compositions by mixing them with hydroxyl endblocked polydiorganosiloxanes. These compositions can also contain fillers and curing catalysts.
U.S. Pat. No. 4,503,210 to Von Au discloses mixtures of tri- and tetrafunctional ketoximino silanes and focuses specifically on the usefulness of tetrafunctional ketoximino silanes in sealant formulations.
The problem with known tetrafunctional oximino silanes (i.e., e.g., those based on methyl ethyl ketoxime (MEKO) and acetone oxime) is that they are solids at room temperature. Since such compounds are very sensitive to moisture they decompose easily to semisolids which are difficult to handle. Thus, these materials have a poor shelf life and require special care in their packaging and transporting.
The known tetrafunctional and trifunctional oximino silanes (i.e., e.g., those based on MEKO and acetone oxime) have other drawbacks. Traditionally, when these materials have been combined with silicone polymers the resulting product has been opaque. This has substantially limited the applications in which these materials can be used.
As the applications in which room temperature curing compositions can be utilized continue to increase, the specific kinds of properties required of these compositions continue to change. The art is continually looking for room temperature curing compositions having new desirable properties without the old undesirable properties like opacity and physical state limitations (solids). We have surprisingly discovered that the silanes of the invention satisfy this need in the art.